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Programmable Logic Controllers
2.5.12
PLC components glossary
The following table describes the meaning and functionality of the single components und
parts of a Mitsubishi PLC.
Component
Connection for
expansion
adapter boards
Connection for pro-
gramming units
EEPROM
Memory cassette slot
Extension bus
Analog
potentiometers
Service power supply
Digital inputs
Digital outputs
LEDs for indicating
the input status
LEDs for indicating
the output status
LEDs for indicating
the operating status
Memory battery
RUN/STOP switch
FX Beginners Manual
Description
Optional expansion adapter boards can be connected to this interface. A variety of differ-
ent adapters are available for all FX lines (except the FX
adapters extend the capabilities of the controllers with additional functions or communica-
tions interfaces. The adapter boards are plugged directly into the slot.
This connection can be used for connecting the FX-20P-E hand-held programming unit or
an external PC or notebook with a programming software package (e.g. GX Works2 FX).
Read/write memory in which the PLC program can be stored and read with the program-
ming software. This solid-state memory retains its contents without power, even in the
event of a power failure, and does not need a battery.
Slot for optional memory cassettes. Inserting a memory cassette disables the controller's
internal memory – the controller will then only execute the program stored in the cassette.
Both additional I/O expansion modules and special function modules that add additional
capabilities to the PLC system can be connected here. See chapter 6 for an overview of
the available modules.
The analog potentiometers are used for setting analog setpoint values. The setting can be
polled by the PLC program and used for timers, pulse outputs and other functions (see
Section 4.6.1).
The service power supply (not for FX
DC power supply source for the input signals and the sensors. The capacity of this power
supply depends on the controller model (e.g. FX
400 mA; FX
-16M„-„„ through FX
2N
FX
-64M„-„„: 460 mA)
2N
The digital inputs are used for inputting control signals from the connected switches, but-
tons or sensors. These inputs can read the values ON (power signal on) and OFF (no
power signal).
You can connect a variety of different actuators and other devices to these outputs,
depending on the nature of your application and the output type.
These LEDs show which inputs are currently connected to a power signal, i.e. a defined
voltage. When a signal is applied to an input the corresponding LED lights up, indicating
that the state of the input is ON.
These LEDs show the current ON/OFF states of the digital outputs. These outputs can
switch a variety of different voltages and currents depending on the model and output
type.
The LEDs RUN, POWER and ERROR show the current status of the controller. POWER
shows that the power is switched on, RUN lights up when the PLC program is being exe-
cuted and ERROR lights up when an error or malfunction is registered.
The battery protects the contents of the MELSELC PLC's volatile RAM memory in the
event of a power failure (FX
2N
latched ranges for timers, counters and relays. In addition to this it also provides power for
the integrated real-time clock when the PLC's power supply is switched off.
MELSEC PLCs have two operating modes, RUN and STOP. The RUN/STOP switch
allows you to switch between these two modes manually.
In RUN mode the PLC executes the program stored in its memory.
In STOP mode program execution is stopped.
2NC
, FX
and FX
2NC
3GC
3UC
, FX
, FX
1S
1N
-32M„-„„: 250 mA, FX
2N
, FX2
, FX
, FX
and FX
NC
3GC
3U
Controller Design
and the FX
). These
3GC
) provides a regulated 24V
, FX
and FX
:
3G
3GE
3S
-48M„-„„ through
2N
c only). It protects the
3U
2 – 13
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